Light gray background in "bounce area" of a UITableView

Setting transparencies is bad for performance. What you want is the gray area above the search bar, but it should still be white beyond the end of the list.

You can add a subview to your UITableView that lives above the content instead.

CGRect frame = self.list.bounds;
frame.origin.y = -frame.size.height;
UIView* grayView = [[UIView alloc] initWithFrame:frame];
grayView.backgroundColor = [UIColor grayColor];
[self.listView addSubview:grayView];
[grayView release];

You could add more fancy stuff to the view if you like, perhaps a fade, or a divider line without subclassing UISearchBar.

To extend on HusseinB's suggestion:

Swift 3

let bgView = UIView()
bgView.backgroundColor = UIColor.white
self.tableView.backgroundView = bgView

Objective C

UIView *bgView = [UIView new];
bgView.backgroundColor = [UIColor whiteColor];
[self.tableView setBackgroundView:bgView];

This is one of my very favorite tricks.

UIView *topview = [[[UIView alloc] initWithFrame:CGRectMake(0,-480,320,480)] autorelease];
topview.backgroundColor = [UIColor colorWithRed:226.0/255.0 green:231.0/255.0 blue:238.0/255.0 alpha:1];

[self.tableView addSubview:topview];

Basically you're creating a big view the size of the screen and placing it "above" the content area. You'll never be able to scroll up past it.

And don't worry about the memory impact of a UIView that's 320x480 pixels, it won't consume any significant memory because the CALayer doesn't have any meaningful content.

NOTE: Why is this answer relevant when the "accepted" answer is so much simpler? Why not just set the backgroundView on the table view? It's because, in the case of the Contacts app as shown in the original question, the area "above" the table view has a different background color (light blue) than the area "below" the table view (white). This technique allows you to have two different colors above and below the table view, which cannot be accomplished by a simple background.

EDIT 1/2018: As Tom in the comments pointed out, this answer is quite old and assumes that all iOS devices have the same screen size (seems crazy but it was the case in 2009 when I answered this). The concept I present here still works, but you should use UIScreen.main.bounds to figure out the actual screen size, or you could get into some fancy auto layout stuff (suggestions welcome). I don't recommend using tableView.bounds as in another answer, because typically in viewDidLoad the size of your views is not necessarily the size that they will become after the controller resizes them. Sometimes they start out as 0x0!